VERY CONFUSED over Eevee Light's shadow generation from a Bake Indirect Lighting perspective

VERY CONFUSED over Eevee Light’s shadow generation from a Bake Indirect Lighting perspective.

Ok, during the old OLD days of the scanline renderer, I understand why we need lights that INSIST on generating its own shadows, that makes sense since there are not global illumination/path tracing involved.

When doing outdoor scene in Eevee without the need to press the “Bake Indirect Lighting” button [without the need for irradiance volume], yes, checking the Shadow and Contact Shadow makes sense.

BUT BUT BUT !!!

For indoor scene when we are using the irradiance volume and the “Bake Indirect Lighting” button, isn’t/shouldn’t the various shades of shadow derived MERELY from the various absent of light in an area ?

Just like path tracing renderers, lights that needs to forcibly artificially “create” a shadow makes no sense because the indirect lighting will hereby CREATE the actual REAL shadows.

Doesn’t having lights in Eevee generating its own shadow in an interior scene where irradiance volume already calculated the bounce light kind of “doubling” the shadow effect which shouldn’t be ?

Very confused about the usage of light shadows in indoor lighting in Eevee, please someone explain this to me.

Should we even turn light shadow on for indoor with bake indirect already turned on ?

Baked Indirect Lighting corresponds to one frame.
It is not dynamic and able to take into account what will move inside the room during an animation, contrary to lights.
If you want to have a correct Indirect lighting updated at each frame. It is probably more easy and satisfying to use Cycles.

Oh you wouldn’t hear any arguments about that from me, 100% agree.

I am asking since irradiance calculations are done and the result contains shadows as a by product {no light reached or different intensity in a region = various shades of shadow}, in a shot where there are no moving things doesn’t turning on shadows for lights in these situations adds a layer of artificial shadow to the already existing correctly approximated shadows from the irradiance calculation ?

No, the the lightprobes only affect indirect lighting. Direct lighting, and the corresponding shadows, are still calculated every frame.

Most of time, shadows from irradiance cache are not accurate if its resolution is low.
They can be very blurred and according to intensity you assign to irradiance cache, they can be insufficient.
Shadows from lights may be necessary to fix this.
To obtain a more accurate gradient or sharper shadows of a small object ignored by low resolution of cache.
If object is in foreground of render, you may expect a strong and sharp shadow. It does not matter if scene is indoor or outdoor.

You will not had dozen of irradiance volumes with highest quality settings possible in a scene when you can bake Cycles GI and shadows to textures.

That is a trade off about speed of rendering and quality of result.

But if you are happy with result of irradiance cache ; you can disable shadow of a light.
That is up to you to choose where it is pertinent and where it is not.
If there is a checkbox to disable shadow of light ; it is because both cases are considered useful.

I am simply curious about the logic of overlaying GI shadows with more shadows from light’s artificially calculated ones, it make my brain hurts.

Thanks.

I’m not an Eevee user, but I don’t see the problem of having shadow settings for the direct (live) stuff separated from any shadow settings from indirect (baked) stuff. You may want to rely on irradiance cache for everything indirect, whilst being able to move the light in real time without rebaking everything. Not an issue for seconds worth of bake time, but will hurt you if baking takes hours.

Thank you Carl.